sjm@dayton.UUCP (Steven J. McDowall) (01/26/86)
*** For the line eater *** Ok..I'm working on the following problem for one of my classes, and can not find/figure out an "easy" way to solve it. We are given a process that occurs 600 times/hour, and are to calculate the following probabilities: (The first 2 are easy) a) That there will be exactly 0 occurences in 3 minutes. b) That there will be exactly 60 occurences in 3 minutes. Now for the tough one: c) If a switch board can handle 20 calls per minute, that what is the probability that it will be overrun in 3 minutes with a 600 call/hour poisson distribution? (Ie: that there will be at least 1 minute with at least 21 calls?) It seems to me that the way to solve it would be to calculate SIGMA(P63(3)) (Ie..SUm of the probabilities of 0-63 events) and subtract 1, giving the probability of more than 63 events in 3 minutes (which means that we had* to have 1 minute with more than 21, yes?) However, *summing* that damn thing is no fun! Especially 63 cases! By the bye, in case you forget Pn(t) = [(rt)^n/n!] * e^(-rt) where r = rate and t = time...n is the number of occurances exactly*. Thanks! -- Steven J. McDowall Dayton-Hudson Dept. Store. Co. UUCP: ihnp4!rosevax!dayton!sjm 700 on the Mall ATT: 1 612 375 2816 Mpls, Mn. 55408